The present invention relates to a glazing for minimizing or preventing bird collisions with windows or other glazings. The invention further relates to a method of manufacturing such a glazing.
Bird deaths due to window strikes represent one of the greatest threats to avian mortality next to habitat destruction. Due to the reflective and transparent characteristics of glass, the glass is not perceived as a barrier to the bird. The bird does not recognize that reflections of, for example, the sky, other buildings, vegetation and even open space, are false. As a result, the bird flies into the glass. Typically, the glass is a glazing in a building, for example, a window, but could equally be a glass balcony, a glazed door, etc.
Many millions of birds die each year from collisions with glass on buildings. While songbirds are most at risk from collisions with glass, nearly 300 species have been reported as collision victims, including hummingbirds, woodpeckers, kingfishers, waders and birds of prey. It is likely that these numbers will grow as advances in glass technology and production make it possible to construct buildings with all-glass curtain walls, in addition to the general increase in the amount of glass being used in architecture.
The reduction of bird strikes can be achieved in a number of ways. A common approach involves creating a visual signal that alerts the birds to the presence of the glass. Known techniques include the use of fritting, i.e. the placement of ceramic lines or dots on glass, the use of screens, latticework, or grilles. More recently however, it has been shown that the use of ultraviolet (UV) patterns on glass may help birds to detect the presence of the glass.
Many families of birds are tetrachromatic, possessing four types of cone cells each with a distinctive maximal absorption peak. In some bird families, the maximal absorption peak of the cone cell responsible for the shortest wavelength extends to the UV range, making them UV-sensitive. As such, many birds are able to see into the UV spectrum, in particular in the range 300 to 400 nm, a range largely invisible to humans.
A UV reflective coated glass for preventing bird collisions is known under the registered trade mark Ornilux Mikado®. The glass has a UV patterned coating which is visible to birds but substantially invisible to the human eye. However, it is a disadvantage of such a glazing in that it relies only on a UV-reflective coating, and it is believed that in order to be an effective bird deterrent, UV patterns need to have a strong contrast.
Thus, in WO 2014/188196 A1 a bird safe glazing was described in which a glass substrate was provided with an antireflection coating, such as that found on the Pilkington Optiview™ coated glass product, and a striped TiO2 coating was produced thereover by TiO2 deposition through a mask in contact with the glass substrate. The reflective TiO2 not only provided enhanced UV reflectance, but also destroyed the antireflective effect of the antireflection coating at the stripe location. This provided a dual enhancement of the UV pattern. Consequently, birds readily saw the sharp-edged contrasting stripe pattern and the risk of bird collision with the glazing was minimized.
However, a disadvantage of using TiO2 stripes to preferentially reflect UV light is that they also reflect and absorb visible radiation, though to a lesser extent. FIG. 1 shows a glazing 1 according to an embodiment of WO 2014/188196 A1. The glazing includes comprises a substrate 4 having a first surface 8 and a second surface 10. An antireflection coating 12 is provided directly on to the first surface 8, and a UV reflectance coating 14 is provided on top of the antireflection coating 12 in a patterned arrangement comprising a plurality of stripes 14. The stripes 14 are formed by a coating process utilizing a mask in contact with the substrate, resulting in stripes 14 that are substantially rectangular in profile with sharp edges 15. This means that although the stripes are substantially transparent, they can be perceived by humans.